NOTE: Where it is feasible, a syllabus (headnote) will be released, as is being done in connection with this case, at the time the opinion is issued.The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience of the reader.See United States v. Detroit Timber & Lumber Co.,
200 U. S. 321
.

SUPREME COURT OF THE UNITED STATES

S. D. WARREN CO. v. MAINE BOARD OF ENVIRONMENTAL PROTECTION et al.

certiorari to the supreme judicial court of maine

No. 04–1527. Argued February 21, 2006—Decided May 15, 2006

Petitioner company (Warren) asked the Federal Energy Regulatory Commission (FERC) to renew federal licenses for five of the hydroelectric dams it operates on a Maine river to generate power for its paper mill. Each dam impounds water, which is then run through turbines and returned to the riverbed, passing around a section of the river. Under protest, Warren applied for water quality certifications from respondent Maine Board of Environmental Protection pursuant to §401 of the Clean Water Act, which requires state approval of “any activity” “which may result in any discharge into the [Nation’s] navigable waters.” FERC licensed the dams subject to compliance with those certifications, which require Warren to maintain a minimum stream flow and to allow passage for certain fish and eels. After losing state administrative appeals, Warren filed suit in a state court, which rejected Warren’s claim that its dams do not result in a “discharge” under §401. The State Supreme Judicial Court affirmed.

Held: Because a dam raises a potential for a discharge, §401 is triggered and state certification is required. Pp. 3–15.

(a) The Clean Water Act does not define “discharge,” but provides that the term “when used without qualification includes a discharge of a pollutant, and a discharge of pollutants,”
33 U. S. C. §1362(16). But “discharge” is presumably broader, else superfluous, and since it is neither defined nor a term of art, it should be construed “in accordance with its ordinary or natural meaning,” FDIC v. Meyer,510 U. S. 471
. When applied to water, discharge commonly means “flowing or issuing out,” Webster’s New International Dictionary 742. This Court has consistently intended that meaning in prior water cases, including the only case focused on §401, PUD No. 1 of Jefferson Cty. v. Washington Dept. of Ecology,511 U. S. 700
, in which no one questioned that the discharge of water from a dam fell within §401’s ambit. The Environmental Protection Agency and FERC have also regularly read “discharge” to cover releases from hydroelectric dams. Pp. 3–6.

(b) Warren’s three arguments for avoiding this common reading are unavailing. The canon noscitur a sociis—“a word is known by the company it keeps,” Gustafson v. Alloyd Co.,513 U. S. 561
—does not apply here. Warren claims that since “discharge” is keeping company with “discharge” defined as adding one or more pollutants, see §1362(12), discharge standing alone must also require the addition of something foreign to the water. This argument seems to assume that pairing a broad statutory term with a narrow one shrinks the broad one, but there is no such general usage of language this way. Warren also relies on South Fla. Water Management Dist. v. Miccosukee Tribe,541 U. S. 95
, but that case is not on point. It addressed §402, not §401, and the two sections are not interchangeable, as they serve different purposes and use different language to reach them. Thus, that something must be added in order to implicate §402 does not explain what suffices for a discharge under §401. Finally, the Clean Water Act’s legislative history, if it means anything, goes against Warren’s reading of “discharge.” Pp. 6–12.

(c) Warren’s arguments against reading “discharge” in its common sense also miss the forest for the trees. Congress passed the Clean Water Act to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters,”
33 U. S. C. §1251(a), the “national goal” being to achieve “water quality [providing] for the protection and propagation of fish … and … for recreation,” §1251(a)(2). To do this, the Act deals with “pollution” generally, see §1251(b), which it defines as “the man-made or man-induced alteration of the [water’s] chemical, physical, biological, and radiological integrity,” §1362(19). Because the alteration of water quality as thus defined is a risk inherent in limiting river flow and releasing water through turbines, changes in the river’s flow, movement, and circulation fall within a State’s legitimate legislative business. State certifications under §401 are essential in the scheme to preserve state authority to address the broad range of pollution. Reading §401 to give “discharge” its common and ordinary meaning preserves the state authority apparently intended. Pp. 12–15.

2005 ME 27, 868 A. 2d 210, affirmed.

Souter, J., delivered the opinion of the Court, in which Roberts, C. J., and Stevens, Kennedy, Thomas, Ginsburg, Breyer, and Alito, JJ., joined, and in which Scalia, J., joined as to all but Part III–C.